This project concerns the molecules that inhibit formation of crystals in human kidneys. Males who form stones differ from normal males in producing urine less effective in slowing the growth of calcium oxalate crystals, and in which the distance between supersaturation and the supersaturation needed to produce crystallization (upper limit of metastability, ULM) is reduced for both calcium oxalate and calcium phosphate. A parallel study is proposed in women, to determine if their mechanisms of stones differ from those in men, and in family members of the male stone formers we have already characterized, to determine if reduced growth inhibition and ULM to supersaturation distance is familial. In collaboration with Project 2, we propose to determine if reduced inhibitions correlate with Randall's plaque number and surface area. Given the male growth inhibition defect, we propose to identify molecules responsible by pursuing our initial observation of aberrant calgranulin molecular size distribution and specific growth inhibition activity, and by contrasting proteins bound to calcium oxalate crystals brought to equivalent degrees of growth inhibition by patient and control dialyzed urine molecules. We will explore the possibility that crystallization in urine consumes high affinity inhibitors reducing their availability, by determining the effects of EDTA dissolution on growth inhibition by urine molecules. Finally, we plan similar experiments to identify molecules responsible for the reduced ULM to supersaturation distance by contrasting molecules from patients and normals bound to the calcium oxalate and calcium phosphate crystals produced as their urine supersaturation is raised above the ULM in vitro. We will also explore the possibility that reduced urine pyrophosphate or an abnormal relationship between urine citrate and urine pH may contribute to the reduced ULM in patients.